To cope with miniaturization and cost reduction of mobile computing devices such as smart phones, thinning of silicon wafers to be chip substrates and shifting to larger plastic substrates for improving production efficiency have been investigated recently in the semiconductor industry. In thinner substrates and flexible plastic substrates, however, influence of warpage becomes serious, and accordingly, the strength of encapsulant is important so as not to cause crack in the encapsulant. To improve the strength of encapsulant, various investigations have been carried out using a curing agent including a phenol compound such as bisphenol A and biphenyl or a phenol resin such as a novolak resin and a cresol novolak resin (Patent Literature 1), but encapsulant with more increased strength has been desired. Being flexible, the substrate is liable to bend. In such bending, the end of chip and the lower part of chip are subjected to large stress, and are liable to cause peeling between the encapsulant and the chip or the encapsulant and the substrate. Accordingly, there has been arising necessity to improve adhesion of encapsulant itself and need for decreasing warpage due to cure shrinkage.
In order to improve production efficiency, square substrates are frequently used as the plastic substrate. When such a square plastic substrate is encapsulated, liquid type encapsulant is liable to cause unevenness about the inside and outside of the substrate. To encapsulate this substrate easily and uniformly, film type encapsulant has been desired.
Accordingly, it has been desired to develop a highly adhesive resin composition with improved strength that can reduce warpage and does not cause peeling even in warping, a wafer mold material with excellent property for protecting a wafer using the same, and a film formed from the material, so as not to cause crack in bending.